Raw material prices for wood have been steadily climbing in recent years with little expectation of a significant drop in the commodity price. Concurrently, a requirement for non-rot millwork-type building components has developed within the window and door industry (as well as within the overall construction industry). In response to these conditions, various manufacturers of window lineal components who previously extruded sash or other profiles of solid PVC have recently developed cellular PVC sash profiles using either the "Free Foam" or "Celuka" foam extrusion process (discrete/single self-skinning PVC foam extrusion).
Structural integrity (as defined by ASTM E330, Procedure A) of such cellular (foam) PVC sash members has so far been less than adequate, and such products have not proven to be able to consistently meet minimum DP grades required by the industry. One possible solution for this could be a co-extruded cellular sash member whose exterior surface has a co-extruded rigid PVC wall and the remaining (interior) profile body is foamed PVC (see FIG. 1); however, the reduced cost benefits inherent to extruded cellular PVC components are largely or even completely lost with this design. Thus, while this design does provide increased structural integrity, there may not be a great deal of other market advantage in producing such a cellular sash with a rigid exterior wall.